Human and Insect Agriculture Codebook, Version 2 (20NOV14) Species / Culture __Fungus-Farming Ants______________________________________________________ Coder __Ted Schultz________________________________________________________________________ Comments: I have created three columns for coding: (i) lower fungus-farming ants (e.g., Cyphomyrmex longiscapus), (ii) non-leaf-cutting higher attine ants (e.g., Trachymyrmex septentrionalis), and (iii) leaf-cutter ants (e.g., Atta cephalotes). I have done this to more accurately reflect transitions that take place in fungus-farming ant evolution subsequent to the origin of farming. For variables that compare non-agriculturalists to agriculturalists, I have, for column (i), compared lower fungus-farming ants to their closest non-fungus-farming relatives, the dacetine ants (including Lenomyrmex, Acanthognathus, and Daceton, among others). In scoring column ii, however, I have compared non-leaf-cutting higher-attine ants with lower attine ants, and in scoring column iii, I have compared leaf-cutter ants to non-leaf-cutting higher-attine ants. While this may sound confusing in the abstract, I think that it is easy to understand when examining the scoring and that it best reflects the purpose of the scoring. (In the human analogy, comparing lower fungus-farming ants with leaf-cutter ants is like comparing subsistence agriculture with industrial-scale agriculture, with the non-leaf-cutting higher fungus- farmers somewhere in between. I have interpreted "community" to mean "colony" and this works out for most variables, but for some variables it may introduce problems. An ant colony is, functionally, an organism, so when it comes to, e.g., population- biological questions about birth and death rates or density dependence, it is probably better to think at the level of a colony within a population of colonies rather than an individual within a single colony. Given this problem, my scores should be considered tentative and may require correction. Variables Comments and references I. “Agricultural” practice variables VI.1 Selecting substrate (universal) 1 = low specificity 2 = moderate specificity 3 = high specificity 9 = missing COMMENTS: Species-specific data are hard to come by, but in general "lower" attines harvest a mixture of insect frass, seeds, flower stamens, and other detritus of plant origin that is presumably not yet invaded by other microbes (fungi or bacteria). Transitional "higher" attines such as Trachymyrmex and Sericomyrmex species may also forage for most of these substrates, but some (most? all?) species may also cut tender shoots of fresh vegetation (flower petals, flower stamens). In the early stages of colony foundation, leaf-cutting ants (Atta and especially Acromyrmex spp.) may also take frass and other non-cut substrates, but mature colonies tend to focus entirely on cut vegetation (leaves in some species, grasses in others). So scoring depends strongly on what is meant by "specificity," but since there is an apparent evolutionary gradation from lower to higher specificity, I am scoring this 1/2/3. VI.2 Internal sustainability (harvested domesticates provide source for next crop cycle) 1 = 0 to 33% 2 = 34 to 67% 3 = 68 to 100% 9 = missing COMMENTS: I would guess that daughter nests obtain domesticates from the maternal nest 99% of the time. Over evolutionary time scales, however, replacement fungi are acquired either from the wild or from nests of other fungus-farming ants. But all cultivars are drawn from a limited group of species in the tribe Leucocoprineae (except for a large clade of species in the genus Apterostigma, which cultivates pterulaceous fungi). VI.3 Planting crops 1 = low investment 2 = moderate investment 3 = high investment 9 = missing COMMENTS: The ants are obligate agriculturalists. VI.4 Preparing substrate 1 = low investment 2 = moderate investment 3 = high investment 9 = missing VI.5 Dimensions of substrate 2 Variables Comments and references 1 = 2d 2 = 3d 9 = missing VI.6 Temporal variation in cultivation 1 = discrete (seasonal/crop rotation/fallowing) 2 = continuous 9 = missing COMMENTS: Exceptions occur in temperate-zone species that are constrained to "hibernate" in winter months, but these are the exceptions to the rule. VI.7 Diversity of domesticates (at a single location/within a single group) 1 = single domesticate 2 = two or three domesticates 3 = four or more domesticates 9 = missing COMMENTS: There is one domesticate strain in a given colony at a given time (and usually for the entire life of the colony). VI.8 Monitoring crops for disease or thieves/predators 1 = 0 to 33% of the time 2 = 34 to 67% of the time 3 = 68 to 100% of the time 9 = missing COMMENTS: Intensive monitoring. VI.9 “Weeding”: Physical removal of invasive pests/predators 1 = 0 to 33% of pests removed 2 = 34 to 67% of pests removed 3 = 68 to 100% of pests removed 9 = missing COMMENTS: Intensive weeding. VI.10 Engineering for optimal growth condition (climate control, watering, etc.) 1 = low investment 2 = moderate investment 3 = high investment 3 Variables Comments and references 9 = missing COMMENTS: Wet-forest-dwelling fungus-farming ants may require the least amount of work to make their gardens happy, but even they have to worry about, e.g., too much moisture. VI.11 Pests: Chemical control 1 = 0 to 33% of crops treated 2 = 34 to 67% of crops treated 3 = 68 to 100% of crops treated 9 = missing COMMENTS: Guesses. The true extent of chemical control (originating in the metapleural gland, possibly the mandibular gland) is unknown. References include Fernandes-Marin, Bot et al., others. VI.12 Pests: Microbial control 1 = 0 to 33% of crops treated 2 = 34 to 67% of crops treated 3 = 68 to 100% of crops treated 9 = missing COMMENTS: Guesses. References to come. VI.13 Fertilizing: Organic 1 = 0 to 33% of crops treated 2 = 34 to 67% of crops treated 3 = 68 to 100% of crops treated 9 = missing COMMENTS: This is unclear relative to attine ants. All substrates are organic. In some (all?) species fecal droplets are applied, but their purpose is unclear and may be to provide digestive enzymes originating from the fungus. (Ref. Martin, Bot et al.) VI.14 Fertilizing: Synthetic chemical 1 = 0 to 33% of crops treated 2 = 34 to 67% of crops treated 3 = 68 to 100% of crops treated 9 = missing COMMENTS: That's a human thing. VI.15 Reproductive isolation from free- living populations (reproductive barriers) 1 = low isolation 2 = moderate isolation 3 = high isolation 9 = missing 4 Variables Comments and references COMMENTS: This is a very important variable and is poorly understood in most attine ant species. It is important to remember that there are at least two types of free-living populations: (i) genuinely wild- type (ancestral) populations from which the original domesticates were drawn and (ii) populations of "escaped" domesticates. If domestication favors alleles, gene combinations, or other genetic modifications that differ from those present in wild populations (which is almost the definition of "domestication"), then interbreeding with ancestral wild-type (type i) populations will dilute those modifications, whereas interbreeding with type ii wild populations will not, unless the type ii population is sufficiently old and/or selection pressures in the wild greatly differ from selection pressures under domestication. In the case of interbreeding with type i populations, the degree of dilution will vary depending on: (i) the relative effective sizes of the wild and domesticated populations, (ii) the difference between domesticated and wild selection regimes, (iii) the strength of selection in each regime, (iv) the degree of interbreeding (rare vs. common). The current paradigm is that lower attines reacquire their fungi from the wild frequently over evolutionary time periods, but even in lower attine species we have discovered evidence for long-term associations with particular fungal species, suggesting that, when fungi are reacquired, they are reacquired with prejudice, so the ants may be exerting strong selection pressures on single fungal species, in effect "domesticating" the entire wild population, at least on local geographic scales. VI.16 Controlling breeding partners (controlling recombination and sexual selection) 1 = low control 2 = moderate control 3 = extensive control 9 = missing COMMENTS: This is poorly studied, but it is clear that over ecological time periods (multiple ant and fungal generations) the ants are exerting total control over fungal mating, essentially preventing it. In higher attines there are no known wild populations of fungi, yet fungal sex occurs. VI.17 Artificial selection for domesticate improvement 1 = no selection performed 2 = selection done, but less than annually 3 = selection common (annually or more frequent) 9 = missing COMMENTS: The ant equivalent of artificial selection must have occurred in the higher attine ants because the fungi are clearly genetically modified relative to their ancestors (e.g., they are polyploid), although this could also be described as coevolution or symbiotic evolution rather than artificial selection exerted by the ants on their associated fungi. Because artificial selection is usually thought to require intent, I am scoring this 9/9/9. 5 Variables Comments and references VI.18 Genetic engineering for domesticate improvement (e.g. GMO) 1 = absent 2 = present 9 = missing COMMENTS: The higher attine domesticates are polyploid, but this does not qualify as deliberate, human-style "genetic engineering." Score: